Imports System
Imports System.Runtime.InteropServices
Imports System.Drawing
Imports System.Drawing.Imaging


Namespace ScreenShotDemo
    _
   '/ <summary>
   '/ Provides functions to capture the entire screen, or a particular window, and save it to a file.
   '/ </summary>
   Public Class ScreenCapture
      
      '/ <summary>
      '/ Creates an Image object containing a screen shot of the entire desktop
      '/ </summary>
      '/ <returns></returns>
      Public Function CaptureScreen() As Image
         Return CaptureWindow(User32.GetDesktopWindow())
      End Function 'CaptureScreen
      
      
      '/ <summary>
      '/ Creates an Image object containing a screen shot of a specific window
      '/ </summary>
      '/ <param name="handle">The handle to the window. (In windows forms, this is obtained by the Handle property)</param>
      '/ <returns></returns>
      Public Function CaptureWindow(handle As IntPtr) As Image
         ' get te hDC of the target window
         Dim hdcSrc As IntPtr = User32.GetWindowDC(handle)
         ' get the size
         Dim windowRect As New User32.RECT()
         User32.GetWindowRect(handle, windowRect)
         Dim width As Integer = windowRect.right - windowRect.left
         Dim height As Integer = windowRect.bottom - windowRect.top
         ' create a device context we can copy to
         Dim hdcDest As IntPtr = GDI32.CreateCompatibleDC(hdcSrc)
         ' create a bitmap we can copy it to,
         ' using GetDeviceCaps to get the width/height
         Dim hBitmap As IntPtr = GDI32.CreateCompatibleBitmap(hdcSrc, width, height)
         ' select the bitmap object
         Dim hOld As IntPtr = GDI32.SelectObject(hdcDest, hBitmap)
         ' bitblt over
         GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, GDI32.SRCCOPY)
         ' restore selection
         GDI32.SelectObject(hdcDest, hOld)
         ' clean up 
         GDI32.DeleteDC(hdcDest)
         User32.ReleaseDC(handle, hdcSrc)
         
         ' get a .NET image object for it
         Dim img As Image = Image.FromHbitmap(hBitmap)
         ' free up the Bitmap object
         GDI32.DeleteObject(hBitmap)
         
         Return img
      End Function 'CaptureWindow
      
      
      '/ <summary>
      '/ Captures a screen shot of a specific window, and saves it to a file
      '/ </summary>
      '/ <param name="handle"></param>
      '/ <param name="filename"></param>
      '/ <param name="format"></param>
      Public Sub CaptureWindowToFile(handle As IntPtr, filename As String, format As ImageFormat)
         Dim img As Image = CaptureWindow(handle)
         img.Save(filename, format)
      End Sub 'CaptureWindowToFile
      
      
      '/ <summary>
      '/ Captures a screen shot of the entire desktop, and saves it to a file
      '/ </summary>
      '/ <param name="filename"></param>
      '/ <param name="format"></param>
      Public Sub CaptureScreenToFile(filename As String, format As ImageFormat)
         Dim img As Image = CaptureScreen()
         img.Save(filename, format)
      End Sub 'CaptureScreenToFile
       _
      
      '/ <summary>
      '/ Helper class containing Gdi32 API functions
      '/ </summary>
      Private Class GDI32
         
         Public SRCCOPY As Integer = &HCC0020
          ' BitBlt dwRop parameter
         Public Shared<DllImport("gdi32.dll")>  _
         Function BitBlt(hObject As IntPtr, nXDest As Integer, nYDest As Integer, nWidth As Integer, nHeight As Integer, hObjectSource As IntPtr, nXSrc As Integer, nYSrc As Integer, dwRop As Integer) As Boolean
         
         Public Shared<DllImport("gdi32.dll")>  _
         Function CreateCompatibleBitmap(hDC As IntPtr, nWidth As Integer, nHeight As Integer) As IntPtr
         
         Public Shared<DllImport("gdi32.dll")>  _
         Function CreateCompatibleDC(hDC As IntPtr) As IntPtr
         
         Public Shared<DllImport("gdi32.dll")>  _
         Function DeleteDC(hDC As IntPtr) As Boolean
         
         Public Shared<DllImport("gdi32.dll")>  _
         Function DeleteObject(hObject As IntPtr) As Boolean
         
         Public Shared<DllImport("gdi32.dll")>  _
         Function SelectObject(hDC As IntPtr, hObject As IntPtr) As IntPtr
      End Class 'GDI32
       _
      
      '/ <summary>
      '/ Helper class containing User32 API functions
      '/ </summary>
      Private Class User32
         <StructLayout(LayoutKind.Sequential)>  _
         Public Structure RECT
            Public left As Integer
            Public top As Integer
            Public right As Integer
            Public bottom As Integer
         End Structure 'RECT
         
         
         Public Shared<DllImport("user32.dll")>  _
         Function GetDesktopWindow() As IntPtr
         
         Public Shared<DllImport("user32.dll")>  _
         Function GetWindowDC(hWnd As IntPtr) As IntPtr
         
         Public Shared<DllImport("user32.dll")>  _
         Function ReleaseDC(hWnd As IntPtr, hDC As IntPtr) As IntPtr
         
         Public Shared<DllImport("user32.dll")>  _
         Function GetWindowRect(hWnd As IntPtr, ByRef rect As RECT) As IntPtr
      End Class 'User32
   End Class 'ScreenCapture 
End Namespace 'ScreenShotDemo
